CN108253650B - A kind of control method of critical-cross carbon dioxide combined heat-pump system - Google Patents

A kind of control method of critical-cross carbon dioxide combined heat-pump system Download PDF

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Publication number
CN108253650B
CN108253650B CN201810049983.6A CN201810049983A CN108253650B CN 108253650 B CN108253650 B CN 108253650B CN 201810049983 A CN201810049983 A CN 201810049983A CN 108253650 B CN108253650 B CN 108253650B
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air cooling
main road
recombiner
bypass
compressor
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CN108253650A (en
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曹锋
王静
殷翔
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Xian Jiaotong University
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Xian Jiaotong University
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Priority to US16/618,353 priority patent/US11255579B2/en
Priority to PCT/CN2018/120175 priority patent/WO2019141019A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H4/00—Fluid heaters characterised by the use of heat pumps
    • F24H4/02—Water heaters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
    • F25B25/005—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00 using primary and secondary systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B30/00—Heat pumps
    • F25B30/02—Heat pumps of the compression type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/31—Expansion valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F25B49/022—Compressor control arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/003—Indoor unit with water as a heat sink or heat source
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2339/00—Details of evaporators; Details of condensers
    • F25B2339/04—Details of condensers
    • F25B2339/047—Water-cooled condensers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/06—Several compression cycles arranged in parallel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2500/00—Problems to be solved
    • F25B2500/19—Calculation of parameters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/02—Compressor control
    • F25B2600/025—Compressor control by controlling speed
    • F25B2600/0253—Compressor control by controlling speed with variable speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/11—Fan speed control
    • F25B2600/112—Fan speed control of evaporator fans
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/25—Control of valves
    • F25B2600/2513—Expansion valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2104—Temperatures of an indoor room or compartment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2106—Temperatures of fresh outdoor air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2115—Temperatures of a compressor or the drive means therefor
    • F25B2700/21152—Temperatures of a compressor or the drive means therefor at the discharge side of the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2116—Temperatures of a condenser
    • F25B2700/21161—Temperatures of a condenser of the fluid heated by the condenser
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Heat-Pump Type And Storage Water Heaters (AREA)

Abstract

The invention discloses a kind of control methods of critical-cross carbon dioxide combined heat-pump system, including CO2Main road compressor, air cooling-air cooling recombiner, supercooling-evaporation recombiner, evaporator and CO2Auxiliary compressor；Air cooling-air cooling recombiner includes CO2Main road, CO2Bypass and three, water route access；Supercooling-evaporation recombiner includes CO2Main road super cooled sect and CO2Bypass evaporator section two paths.The present invention meets daily need so that unit application range is wider including two kinds of operating modes according to return water temperature；The heat exchanger of only one refrigerant and water in the present invention compares more existing critical CO2The heat exchanger of three water and refrigerant in combined heat-pump, this circulation waterway are the single circuit of one-in-and-one-out, and system is simple, reduces failure rate；Subsidiary loop of the present invention can enable heat pump water heater system long-time stable reliability service under the conditions of wider load and temperature using frequency-changeable compressor, reduce power consumption, can also reduce the starting current of compressor.

Description

A kind of control method of critical-cross carbon dioxide combined heat-pump system
Technical field
The invention belongs to technical field of heat pumps, in particular to a kind of controlling party of critical-cross carbon dioxide combined heat-pump system Method.
Background technique
The heat in surrounding air can be absorbed in heat pump, by working medium circulation, transfers heat to recirculated water, plays heating Effect.Traditional heat pump uses R134a mostly, and the tradition working medium such as R410a, the feature of environmental protection is poor, faces gradually superseded trend.
Preceding International Institute or Refrigeration chairman G Lorentzen proposes CO2Trans critical cycle is theoretical, it is indicated that it is in art of heat pumps There to be extremely vast potential for future development.CO2Critical-temperature it is very low, be 31.1 DEG C, therefore CO2Heat pump system is generally using across facing Boundary's circulation.CO2Trans critical cycle compressor exhaust temperature is higher (up to 100 DEG C or more), and in Trans-critical cycle area, CO2In cooling There is biggish temperature glide in the process, this temperature glide just matches with required temperature-variable heat source, can be primary by water It is heated to very high temperature and keeps high efficiency, be particularly suitable for household hot-water field.
CO2Difference between trans critical cycle system and traditional subcritical cycle system is: in traditional subcritical system In system, temperature remains unchanged refrigerant in most of region within the condenser, and in CO2It is overcritical in trans critical cycle system Two-phase section presence is had no in pressure area, temperature and pressure is mutually independent variable, and high side pressure variation is to refrigerating capacity, compression Machine power consumption and COP value can also have an impact.
Trans-critical cycle CO2Heat pump cycle has unique advantage, and exothermic process temperature is higher and sizable there are one Temperature glide (about 80~100 DEG C).Research shows that: (1) when evaporating temperature be 0 DEG C, water temperature can be heated to 60 DEG C from 0 DEG C, Its heat pump COP can reach 4.3, reduce on 75% than electric heater and gas heater energy consumption.In cold district, conventional air source The heating capacity and efficiency of heat pump decline quickly with the reduction of environment temperature, and the use of heat pump is restricted.And CO2Heat pump system exists Higher heating load and very high leaving water temperature can be maintained under low temperature environment, greatly save energy spent by ancillary heating equipment Amount.
The performance of trans-critical carbon dioxide heat pump water heater is seriously limited by gas cooler exit temperature, gas cooler Outlet temperature is lower, and system performance is better.When the return water temperature in water circulation system sufficiently low (20 DEG C even lower than 20 DEG C), The gas cooler exit temperature of trans-critical carbon dioxide heat pump water heater also can by circulating water to rather low temperature, This when of system is had excellent performance.However (heat transfer temperature difference, gas cooler outlet are considered when return water temperature is higher than 25 DEG C Carbon dioxide temperature is likely to be breached 30 DEG C), the performance of system can acutely decline with the raising of return water temperature, when return water temperature height The performance of carbon dioxide heat pump system is very poor when 40 DEG C, and heating COP is even below 1.5.
Existing Trans-critical cycle CO2Combined heat-pump return water is divided into two-way, first via return water into auxiliary circulation gas cooler, It is then return to water outlet, the return water of the second road ring follows evaporator into auxiliary, and water after cooling enters the gas cooler of major cycle, It is then return to water outlet.First via water outlet is supplied water together after mixing with the water outlet of the second tunnel to user.
Existing to determine frequency heat pump system using invariable frequency compressor, totally two circuits, need the heat exchange of three refrigerants and water Device, water route, which is distributed, understands extremely complex with connecting, and is easy to appear failure.It can only be run under design conditions and (work as water circulation system In return water temperature sufficiently low (20 DEG C even lower than 20 DEG C) when, the gas cooler of trans-critical carbon dioxide heat pump water heater goes out Mouth temperature can also be had excellent performance by circulating water to rather low temperature, this when of system), circuit when causing to run Flow cannot make corresponding adjustment with the change of operating condition, especially for the compound heat pump product of major-minor grade, fixed The compressor flowrate operating condition more changeable than being difficult to adapt to causes energy waste or reduced performance of the system under off-design behaviour ((consider that heat transfer temperature difference, gas cooler outlet carbon dioxide temperature are likely to be breached 30 DEG C) when return water temperature is higher than 25 DEG C, The performance of system can acutely decline with the raising of return water temperature, the carbon dioxide heat pump system when return water temperature is higher than 40 DEG C Performance is very poor, and heating COP is even below 1.5).
Summary of the invention
The object of the present invention is to provide a kind of control methods of critical-cross carbon dioxide combined heat-pump system, to solve Existing Trans-critical cycle CO2Combined heat-pump performance is seriously limited by gas cooler exit temperature, water route distribution and connect complicated and energy The problem of source wastes, at the same improve it is existing determine frequency heat pump system and use invariable frequency compressor, circuit flow cannot change, especially needle The heat pump product compound to major-minor grade, the status of the fixed compressor flowrate operating condition more changeable than being difficult to adapt to, this hair Bright heat pump is divided into major loop and subsidiary loop；Under general operating condition, when return water temperature is lower (30 DEG C or be lower than 30 DEG C), operation Direct-heating-type heating mode；(it is higher than 30 DEG C) when return water temperature is higher, is converted to circular form heating mode.Both of which is alternately transported Row, effectively improves the shortcomings that existed system can not adapt to variable working condition, avoids existing system property under off-design behaviour Low and to the energy the waste of energy, while reaching the performance for still keeping high under the conditions of multi-state, due to two kinds of moulds The alternating of formula avoids energy waste caused by existing system single mode of operation, and reduces the quantity of heat exchanger, letter The structure for having changed system reduces the probability of failure.
In order to achieve the above purpose, the technical solution adopted by the present invention is that:
A kind of control method of critical-cross carbon dioxide combined heat-pump system, a kind of critical-cross carbon dioxide compound thermal Pumping system, including CO2Main road compressor, air cooling-air cooling recombiner, supercooling-evaporation recombiner, evaporator and CO2Auxiliary compression Machine；Air cooling-air cooling recombiner includes CO2Main road, CO2Bypass and three, water route access；Supercooling-evaporation recombiner includes CO2Main road Super cooled sect and CO2Bypass evaporator section two paths；A kind of critical-cross carbon dioxide combined heat-pump system include major loop and Two circuits of subsidiary loop；Major loop: CO2The outlet of main road compressor connects air cooling-air cooling recombiner CO2The import of main road, Air cooling-air cooling recombiner CO2The outlet of main road connects supercooling-evaporation recombiner CO2Main road super cooled sect import, supercooling-evaporation The CO of recombiner2The import of the outlet connection evaporator of main road super cooled sect, the outlet of evaporator connects CO2Main road compressor into Mouthful；Subsidiary loop: CO2The outlet of auxiliary compressor connects air cooling-air cooling recombiner CO2The import of bypass, air cooling-air cooling are multiple Clutch CO2The outlet of bypass connects supercooling-evaporation recombiner CO2The import of bypass evaporator section, supercooling-evaporation recombiner CO2 The outlet of bypass evaporator section connects CO2The import of auxiliary compressor；Supercooling-is set between evaporation recombiner and evaporator on major loop It is equipped with CO2Main road expansion valve；CO is provided between air cooling-air cooling recombiner and supercooling-evaporation recombiner on subsidiary loop2Auxiliary Expansion valve；
A kind of critical-cross carbon dioxide combined heat-pump system work is under circular form heating mode, the control method Include:
CO2Main circuit compressor work, major loop are opened, CO2Auxiliary compressor work, subsidiary loop are opened；Fan is in Open state；Major loop: CO2Working medium passes through CO by state point a2Reach state point b after the compression of main road compressor, into air cooling- The CO of air cooling recombiner2In main road, the recirculated water in water route is heated, and itself is cooled to suitable temperature and reaches shape State point c then flows through supercooling-evaporation recombiner CO2Main road super cooled sect, with CO2Bypass evaporator section exchanges heat, further cold But cool down, reach state point d, subsequently into CO2Main road expansion valve is expanded, and the low pressure working fluid after expansion reaches state point e, It enters evaporator to be evaporated, absorbs heat, return to state point a, eventually pass back to CO2The import of main road compressor；It assists back Road: CO2Working medium passes through CO by state point f2Reach state point g after the compression of auxiliary compressor, into air cooling-air cooling recombiner CO2In bypass, the recirculated water in water route is heated, and itself cools and reaches state point h, subsequently enters CO2Bypass Expansion valve carries out expansion and reaches state point i, and the low pressure working fluid after expansion enters supercooling-evaporation recombiner CO2Bypass evaporator section, With CO2The heat exchange of main road super cooled sect, further cools down CO2Main road super cooled sect, itself evaporation endothermic reach state point f, eventually pass back to CO2The import of auxiliary compressor.
Further, in air cooling-air cooling recombiner, main road CO2Working medium is in CO2Cooling heat release, bypass CO in main road2Work Matter is in CO2Cooling heat release, recirculated water absorb heat, reach the temperature of setting in bypass；In supercooling-evaporation recombiner, main road CO2Working medium is in CO2Main road super cooled sect further cools down heat release, bypass CO2Working medium is in CO2Bypass evaporator section evaporation endothermic, CO2Bypass Evaporator section and CO2The heat exchange of main road super cooled sect, keeps heat balance.
Further, bypass controls control method: acquisition environment temperature tRing, air cooling set by user-air cooling recombiner CO2The temperature t of bypass outletG, out bypassWith the temperature t of air cooling set by user-air cooling recombiner water route outletReturn water, pass through public affairs Formula calculates CO2The pressure at expulsion of auxiliary compressorBy adjusting CO2The aperture of bypass expansion valve reaches given Pressure；It is calculated from the formula CO2The electric machine frequency f of auxiliary compressorCompressor 6, make the frequency of compressor as operating condition is become Change；
Main road controls control method: acquisition environment temperature tRing, air cooling set by user-air cooling recombiner CO2Main road goes out The temperature t of mouthG, out main roadWith the temperature t of air cooling set by user-air cooling recombiner water route outletReturn water；Then it is calculated by formula CO out2The optimal pressure at expulsion P of main circuit compressorCO2, main road, by adjusting CO2The aperture of main road expansion valve reaches given Pressure；
Further, air cooling-air cooling recombiner includes three inner tubes and an outer tube, and two interior pipelines are as CO2It leads back Road, an interior pipeline is as CO2Bypass, the access between outer tube and three inner tubes are water route；Three inner tubes are in equilateral triangle cloth It sets, it is D that the tube spacing between three inner tubes is identicalL；The identical diameter of three inner tubes is D2, the diameter of outer tube is D1；Two CO2One end of major loop synthesizes a pipe in air cooling-air cooling recombiner outside and connects CO2The exhaust outlet of main circuit compressor, Two CO2The other end of major loop synthesizes a pipe in air cooling-air cooling recombiner outside and connects exhaust outlet CO2Main road supercooling Section；
Tube spacing D between three inner tubesL, three inner tubes diameter D2With the diameter D of outer tube1Relationship are as follows:
DL=1.7D2 (4)
D1/D2=3.7 (5)
Further, fan is also equipped on evaporator.
Further, CO2Auxiliary compressor uses frequency-changeable compressor.
Further, when the temperature of air cooling set by user-air cooling recombiner water route outlet is greater than or equal to 30 DEG C, institute A kind of work of critical-cross carbon dioxide combined heat-pump system is stated under circular form heating mode.
Compared with prior art, the invention has the following beneficial effects:
The present invention provides a kind of Trans-critical cycle CO2Combined heat-pump and its control method, using by heat pump be divided into major loop and The control mode of subsidiary loop；So that under general operating condition, when return water temperature is lower (30 DEG C or be lower than 30 DEG C), directly-heated is run Type heating mode；(it is higher than 30 DEG C) when return water temperature is higher, is converted to circular form heating mode, system is made to adapt to changeable operating condition While, moreover it is possible to achieve the purpose that energy saving.
(it is higher than 30 DEG C) when return water temperature is higher, runs circular form heating mode, main road compressor operating, major loop is beaten It opens, auxiliary route compressor operating, subsidiary loop is opened, and fan is in the open state；It is multiple in the first supercooling-evaporation of subsidiary loop In clutch, the CO of subsidiary loop2Evaporation endothermic, to the CO in major loop2It carries out second to cool down, makes the CO in major loop2Reach Suitable outlet temperature guarantees higher system performance.
Further, in the present invention only one refrigerant and water heat exchanger, that is, the recombiner that is gas-cooled-is gas-cooled.Phase More existing Trans-critical cycle CO2The heat exchanger of three water and refrigerant in combined heat-pump, this circulation waterway are one-in-and-one-out Single circuit, system is simple, reduces failure rate.
Further, it carries out direct-heating-type by controlling two compressors according to the difference of return water temperature in practice and heats mould The conversion of formula and circular form heating mode keeps the application range of heat pump unit wider, and performance is higher.
Further, CO2Belong to inert gas, it is nontoxic non-stimulated；Good safety and chemical stability, safe nothing Poison, it is non-combustible, even if not decomposing generation pernicious gas at high temperature yet；It is 1, CO to global warming potential index GWP2It is not required to Want commercial synthesis, it is only necessary to it extracts in an atmosphere, it is easy to use；Meanwhile it makees atmospheric ozone layer without any broken ring With ODP 0.Also, CO2Superior thermophysical property itself and good migration characteristic are also suitble to it as refrigeration working medium.
Further, the present invention heats mode and uses CO2Heat pump pattern, energy utilization rate is higher, more energy saving.CO2Evaporation Latent heat is larger, and refrigerating effect per unit swept volume is high, has excellent flowing and heat-transfer character, is significantly reduced the size of system, makes whole A system is very compact.
Further, Trans-critical cycle CO2Heat pump cycle has unique advantage, and exothermic process temperature is higher and there are one Sizable temperature glide (about 80~100 DEG C).Its heat pump COP can reach 4.3, drop than electric heater and gas heater energy consumption Low 75% or more.In cold district, the heating capacity and efficiency of conventional air source heat pump decline quickly with the reduction of environment temperature, heat The use of pump is restricted.And CO2Heat pump system can maintain higher heating load at low ambient temperatures, greatly save auxiliary heating Energy spent by equipment.
Further, subsidiary loop can enable heat pump water heater system in wider load and temperature using frequency-changeable compressor Long-time stable reliability service under the conditions of degree reduces power consumption, can also reduce the starting current of compressor.
Further, when return water temperature is higher, CO2The pressure at expulsion of bypass is higher, and heating capacity is bigger, and operational effect is got over It is good.From control principle angle, propose formula (1), for controlling the pressure at expulsion of compressor 6.To guarantee whole system High performance operation.
Further, the temperature in circulation at d needs to remain suitable value, can be with for the power consumption of equalizing compressor 6 Make the frequency of compressor as operating condition is changed, the optimal frequency of compressor 6 is calculated by formula (2), is compressed by control The revolving speed of machine 6 makes system keep efficient operation.
Further, the optimal pressure at expulsion that compressor 1 can be calculated using formula (3), can allow major loop always Keep the operation of greater efficiency.
Further, using formula (4), (5) can select highest air cooling-air cooling recombiner of heat exchange efficiency, improve The whole performance of system.
Detailed description of the invention
Fig. 1 is a kind of structural schematic diagram of critical-cross carbon dioxide combined heat-pump system of the present invention；
Fig. 2 is the structural representation under a kind of critical-cross carbon dioxide combined heat-pump system direct-heating-type heating mode of the present invention Figure；
Fig. 3 is the circulation signal under a kind of critical-cross carbon dioxide combined heat-pump system direct-heating-type heating mode of the present invention Figure；
Fig. 4 is the structural representation under a kind of critical-cross carbon dioxide combined heat-pump system circular form heating mode of the present invention Figure；
Fig. 5 is the circulation signal under a kind of critical-cross carbon dioxide combined heat-pump system circular form heating mode of the present invention Figure；
Fig. 6 is a kind of internal duct of the air cooling of critical-cross carbon dioxide combined heat-pump system-air cooling recombiner of the present invention Arrangement schematic diagram；
Wherein: 1, CO2Main road compressor；2, air cooling-air cooling recombiner；3, supercooling-evaporation recombiner；4,CO2Main road expansion Valve；5, evaporator；6,CO2Auxiliary compressor；7,CO2Auxiliary expansion valve；8, fan；9,CO2Main road；10,CO2Bypass；11, water Road；12,CO2Main road super cooled sect；13,CO2Bypass evaporator section.
Specific embodiment
The present invention is described in further detail below in conjunction with the accompanying drawings.
Referring to Fig. 1, a kind of critical-cross carbon dioxide combined heat-pump system of the present invention, including CO2Main road compressor 1, gas Cold-air cooling recombiner 2, supercooling-evaporation recombiner 3, evaporator 5 and CO2Auxiliary compressor 6.
Air cooling-air cooling recombiner 2 includes CO2Main road 9, CO2Bypass 10 and 11 3, water route access；Supercooling-evaporation recombiner 3 include CO2Main road super cooled sect 12 and CO213 two paths of bypass evaporator section.
A kind of critical-cross carbon dioxide combined heat-pump system of the present invention includes two circuits of major loop and subsidiary loop；
Major loop: CO2The outlet of main road compressor 1 connects air cooling-air cooling recombiner 2 CO2The import of main road 9, air cooling- The CO of air cooling recombiner 22The outlet of main road 9 connects supercooling-evaporation recombiner 3 CO212 import of main road super cooled sect, supercooling-evaporation The CO of recombiner 32The import of the outlet connection evaporator 5 of main road super cooled sect 12, the outlet of evaporator 5 connects CO2Main road compressor 1 import；
Subsidiary loop: CO2The outlet of auxiliary compressor 6 connects air cooling-air cooling recombiner 2 CO2The import of bypass 10, gas The CO of cold-air cooling recombiner 22The outlet of bypass 10 connects supercooling-evaporation recombiner 3 CO2The import of bypass evaporator section 13, mistake The CO of cold-evaporation recombiner 32The outlet of bypass evaporator section 13 connects CO2The import of auxiliary compressor 6.
Supercooling-is provided with CO between evaporation recombiner 3 and evaporator 5 on major loop2Main road expansion valve 4；On subsidiary loop CO is provided between air cooling-air cooling recombiner 2 and supercooling-evaporation recombiner 32Auxiliary expansion valve 7.
Fan 8 is also equipped on evaporator 5, by changing the revolving speed of fan, the adjustable suitable coefficient of heat transfer.
CO2Auxiliary compressor 6 uses frequency-changeable compressor.
It please refers to shown in Fig. 6, air cooling-air cooling recombiner 2 includes three inner tubes and an outer tube, two interior pipeline conducts CO2Major loop 9, an interior pipeline is as CO2Bypass 10, the access between outer tube and three inner tubes are water route 11.Three inner tubes are in Equilateral triangle arranges that it is D that the tube spacing between three inner tubes is identicalL；The identical diameter of three inner tubes is D2, the diameter of outer tube For D1.Two CO2One end of major loop 9 synthesizes a pipe in air cooling-air cooling recombiner 2 outside and connects CO2Main circuit compression The exhaust outlet of machine 1, two CO2The other end of major loop 9 synthesizes a pipe in air cooling-air cooling recombiner 2 outside and connects CO2 Main road super cooled sect 12.
In order to guarantee that unit when return water temperature changes, can guarantee suitable CO2Cooling temperature, to guarantee higher System performance, the present invention are provided with two kinds of operational modes:
Direct-heating-type heating mode (return water temperature is 30 DEG C or lower than 30 DEG C): Fig. 2 and Fig. 3, CO are please referred to2Major loop pressure Contracting machine 1 works, and major loop is opened；CO2Auxiliary compressor 6 is closed, and subsidiary loop is closed；Fan is in the open state.Major loop: CO2Working medium passes through CO by state point a2Reach state point b after the compression of main road compressor 1, into air cooling-air cooling recombiner 2 CO2In main road 9, the recirculated water in water route 11 is heated, and itself is cooled to suitable temperature and reaches state point c, so Supercooling-evaporation recombiner 3 CO is flowed through afterwards212 state of main road super cooled sect does not change, and is still state point c, subsequently into CO2It is main Road expansion valve 4 is expanded, and the low pressure working fluid after expansion reaches state point d, is entered evaporator 5 and is evaporated, and heat is absorbed, State point a is returned to, CO is eventually passed back to2The import of main road compressor 1.
Circular form heating mode (return water temperature is higher than 30 DEG C): Fig. 4 and Fig. 5, CO are please referred to2Main circuit compressor 1 works, Major loop is opened, CO2Auxiliary compressor 6 works, and subsidiary loop is opened；Fan is in the open state.Major loop: CO2Working medium is by shape State point a passes through CO2Reach state point b after the compression of main road compressor 1, into air cooling-air cooling recombiner 2 CO2It is right in main road 9 Recirculated water in water route 11 is heated, and itself is cooled to suitable temperature and is reached state point c, and supercooling-steaming is then flowed through Send out the CO of recombiner 32Main road super cooled sect 12, with CO2Bypass evaporator section exchanges heat, and further cools, and reaches state point d, Subsequently into CO2Main road expansion valve 4 is expanded, and the low pressure working fluid after expansion reaches state point e, enters the progress of evaporator 5 Evaporation absorbs heat, returns to state point a, eventually pass back to CO2The import of main road compressor 1.
Subsidiary loop: CO2Working medium passes through CO by state point f2Reach state point g after the compression of auxiliary compressor 6, into gas The CO of cold-air cooling recombiner 22In bypass 10, the recirculated water in water route 11 is heated, and itself cools and reaches shape State point h, subsequently enters CO2Bypass expansion valve 7 carries out expansion and reaches state point i, and the low pressure working fluid after expansion enters supercooling-evaporation The CO of recombiner 32Bypass evaporator section 13, with CO2Main road super cooled sect 12 exchanges heat, and further cools down CO2Main road super cooled sect 12, itself Evaporation endothermic reaches state point f, eventually passes back to CO2The import of auxiliary compressor 6.
In air cooling-air cooling recombiner 2, main road CO2Working medium is in CO2Cooling heat release, bypass CO in main road 92Working medium is in CO2 Cooling heat release, recirculated water absorb heat, reach suitable temperature in bypass 10.In supercooling-evaporation recombiner 3, main road CO2Work Matter is in CO2The further cooling heat release of main road super cooled sect 12, reaches suitable temperature, bypass CO2Working medium is in CO2Bypass evaporator section 13 steams Hair heat absorption, CO2Bypass evaporator section 13 and CO2Main road super cooled sect 12 exchanges heat, and keeps heat balance.
Bypass control: when return water temperature higher (being greater than or equal to 30 DEG C), CO2The pressure at expulsion of bypass is higher, heating Amount is bigger, and operational effect is better.From control principle angle, a CO is proposed2The fitting formula of bypass pressure at expulsion, is used for Control the pressure at expulsion of compressor 6.To guarantee the high performance operation of whole system.As given tG, out bypass(air cooling-air cooling recombiner 2 CO2The temperature that bypass 10 exports), tRing(environment temperature), tReturn water(temperature of air cooling-air cooling recombiner 2 water route 11 outlet) Afterwards, it is calculated by formula(CO2The pressure at expulsion of auxiliary compressor 6), by adjusting CO2Bypass expansion valve 7 is opened Degree is to reach given pressure, to guarantee the more efficient operation of system.The present invention proposes, in operating condition variation, CO2Auxiliary pressure The adaptation resistant frequency of contracting machine 6 controls formula.Temperature in circulation at d needs to remain suitable value, for balanced CO2Auxiliary pressure The power consumption of contracting machine 6 can make the frequency of compressor as operating condition is changed, and so that system is kept efficient operation, propose following Fitting formula.F can be calculated from the formulaCompressor 6(CO2The electric machine frequency of auxiliary compressor 6), the frequency of compressor can be made As operating condition is changed, system is made to keep efficient operation.
Main road control: as given tG, out main road(air cooling-air cooling recombiner 2 CO2The temperature that main road 9 exports), tRing(environment temperature Degree) tReturn water(temperature of air cooling-air cooling recombiner 2 water route 11 outlet), can calculate P by formulaCO2, main road(CO2Major loop The optimal pressure at expulsion of compressor 1), by adjusting CO2The aperture of main road expansion valve 4 reaches given pressure, to guarantee The efficient operation of system.
In order to guarantee CO2Sufficiently exchange heat with water, the invention to propose air cooling-air cooling recombiner structure optimal Parameter:, can be according to parameter D when selecting air cooling-air cooling recombiner 21: outer tube diameter and formula calculate DL: inner tube Between center away from, select be most suitable for this system air cooling-air cooling recombiner.
DL=1.7D2 (4)
D1/D2=3.7 (5).

Claims (4)

1. a kind of control method of critical-cross carbon dioxide combined heat-pump system, which is characterized in that a kind of Trans-critical cycle dioxy Change carbon combined heat-pump system, including CO2Main road compressor (1), air cooling-air cooling recombiner (2), supercooling-evaporation recombiner (3), Evaporator (5) and CO2Auxiliary compressor (6)；Air cooling-air cooling recombiner (2) includes CO2Main road (9), CO2Bypass (10) and water route (11) three accesses；Supercooling-evaporation recombiner (3) includes CO2Main road super cooled sect (12) and CO2Bypass evaporator section (13) two logical Road；A kind of critical-cross carbon dioxide combined heat-pump system includes two circuits of main road and bypass；
Main road: CO2The outlet of main road compressor (1) connects air cooling-air cooling recombiner (2) CO2The import of main road (9), air cooling- The CO of air cooling recombiner (2)2The outlet of main road (9) connects supercooling-evaporation recombiner (3) CO2Main road super cooled sect (12) import, Supercooling-evaporation recombiner (3) CO2The import of outlet connection evaporator (5) of main road super cooled sect (12), evaporator (5) go out Mouth connection CO2The import of main road compressor (1)；
Bypass: CO2The outlet of auxiliary compressor (6) connects air cooling-air cooling recombiner (2) CO2The import of bypass (10), air cooling- Be gas-cooled recombiner (2) CO2The outlet of bypass (10) connects supercooling-evaporation recombiner (3) CO2The import of bypass evaporator section (13), Supercooling-evaporation recombiner (3) CO2The outlet of bypass evaporator section (13) connects CO2The import of auxiliary compressor (6)；
Supercooling-is provided with CO between evaporation recombiner (3) and evaporator (5) on main road2Main road expansion valve (4)；Air cooling-on bypass Air cooling recombiner (2) and supercooling-evaporation recombiner are provided with CO between (3)2Bypass expansion valve (7)；
A kind of critical-cross carbon dioxide combined heat-pump system work is under circular form heating mode, the control method packet It includes:
CO2Main road compressor operating, main road are opened, CO2Auxiliary compressor work, bypass are opened；Fan is in the open state；
Main road: CO2Working medium passes through CO by state point a2Reach state point b after the compression of main road compressor, it is multiple into air cooling-air cooling The CO of clutch2In main road, the recirculated water in water route is heated, and itself is cooled to suitable temperature and reaches state point c, Then flow through supercooling-evaporation recombiner CO2Main road super cooled sect, with CO2Bypass evaporator section exchanges heat, and further cools, Reach state point d, subsequently into CO2Main road expansion valve is expanded, and the low pressure working fluid after expansion reaches state point e, is entered Evaporator is evaporated, and is absorbed heat, is returned to state point a, eventually pass back to CO2The import of main road compressor；
Bypass: CO2Working medium passes through CO by state point f2Reach state point g after the compression of auxiliary compressor, it is multiple into air cooling-air cooling The CO of clutch2In bypass, the recirculated water in water route is heated, and itself cools and reaches state point h, is subsequently entered CO2Bypass expansion valve carries out expansion and reaches state point i, and the low pressure working fluid after expansion enters supercooling-evaporation recombiner CO2Bypass Evaporator section, with CO2The heat exchange of main road super cooled sect, further cools down CO2Main road super cooled sect, itself evaporation endothermic reach state point f, most After return to CO2The import of auxiliary compressor；
Bypass control method: acquisition environment temperature tRing, air cooling set by user-air cooling recombiner CO2The temperature of bypass outlet tG, out bypassWith the temperature t of air cooling set by user-air cooling recombiner water route outletReturn water, CO is calculated by formula (1)2Auxiliary The pressure at expulsion of compressorBy adjusting CO2The aperture of bypass expansion valve (7) reaches given pressure；According to public affairs Formula (2) calculates CO2The electric machine frequency f of auxiliary compressorCompressor 6, make the frequency of compressor as operating condition is changed；
Main road control method: acquisition environment temperature tRing, air cooling set by user-air cooling recombiner CO2The temperature of main road outlet tG, out main roadWith the temperature t of air cooling set by user-air cooling recombiner water route outletReturn water；Then CO is calculated by formula (3)2 The optimal pressure at expulsion P of main road compressorCO2, main road, by adjusting CO2The aperture of main road expansion valve reaches given pressure；
Air cooling-air cooling recombiner (2) includes three inner tubes and an outer tube, and two inner tubes are as CO2Main road (9), an inner tube are made For CO2Bypass (10), the access between outer tube and three inner tubes are water route (11)；Three inner tubes in equilateral triangle arrange, three Tube spacing between inner tube is identical, is DL；The identical diameter of three inner tubes is D2, the diameter of outer tube is D1；Two are used as CO2 Both ends of the inner tube of main road (9) on the outside of air cooling-air cooling recombiner (2) synthesize a pipe, and the pipe of one end connects CO2It is main The pipe of the exhaust outlet of road compressor (1), the other end connects CO2Main road super cooled sect (12)；
Tube spacing D between three inner tubesL, three inner tubes diameter D2With the diameter D of outer tube1Relationship are as follows:
DL=1.7D2 (4)
D1/D2=3.7 (5).
2. control method according to claim 1, which is characterized in that in air cooling-air cooling recombiner, main road CO2Working medium exists CO2Cooling heat release, bypass CO in main road2Working medium is in CO2Cooling heat release, recirculated water absorb heat, reach the temperature of setting in bypass Degree；In supercooling-evaporation recombiner, main road CO2Working medium is in CO2Main road super cooled sect further cools down heat release, bypass CO2Working medium exists CO2Bypass evaporator section evaporation endothermic, CO2Bypass evaporator section and CO2The heat exchange of main road super cooled sect, keeps heat balance.
3. control method according to claim 1, which is characterized in that be also equipped with fan (8) on evaporator (5).
4. control method according to claim 1, which is characterized in that air cooling set by user-air cooling recombiner water route When the temperature of outlet is greater than or equal to 30 DEG C, a kind of critical-cross carbon dioxide combined heat-pump system work is heated in circular form Under mode.
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